The objectives of the proposed investigations are to ascertain the hormonal conditions associated with the initiation of milk secretion. Experiments were designed to determine common hormonal denominators for the induction of lactation and to simulate conditions whereby abnormal lactation occurs in the human. Galactorrhea induced by phenothiazine tranquillizers and after interruption of oral conraceptive use are of particular concern. Concentratios of hormones will be measured by radioligand methods and responses by ammmary tissue will be evaluated by electron microscopy. by RNA/ DNA ratio and by tissue lactose assays. The tissue concentration of steroids will be measured by gas chromatography. Since prostaglandin secretion by the uterus has been shown to rise sharply shortly before parturition, the role of this compound in the release of secretory products from parenchymal cells that occurs within a few hours antepartum will be investigated. Further studies of the mechanisms involved in the induction of lactogenesis are also contemplated for the next year, particularly the synergistic effect of estrogens.